This project seeks to understand the biological function of signaling molecules Pleiotrophin (PTN) and Midkine (MK). PTN and MK have proposed signaling functions in angiogenesis, oncogenesis, and chemotaxis. They are putative ligands for Anaplastic Lymphoma Kinase (ALK), a human proto- oncogene. The Drosophila homologue of ALK, DAIk, mediates visceral mesoderm development, and is activated by the secreted molecule Jelly belly (Jeb). The study seeks to elucidate the developmental roles of PTN and MK by examining the loss-of-function effects of Miple 1 and Miple 2, Drosophila homologues to PTN and MK, during embryogenesis. It will address three topics: the role of PTN and MK in DAIk-mediated visceral mesoderm development, the gain-of-function effects of PTN and MK, and the participation of PTN and MK in other developmentally required signaling pathways.